Ultraviolet lamp



March 7, 1939. p CRAIG 2,150,054

ULTRAVIOLET LAMP Filed May 18, 1933 gmwnfoz PALMER H. CRAIG Patented Mar. 7, 1939 PATENT OFFICE ULTRAVIOLET LAMP Palmer H. Craig, Cincinnati, Ohio, assignor to Invex Corporation, a corporation of New York Application May 18, 1933, Serial No. 671,727

7 Claims.

This invention relates to electric lamps and in particular to lamps for the production of ultra-violet radiations.

While the main object of my invention is to produce a lamp for emitting ultra-violet radiations, a further object is to produce a lamp which may at the same time be employed for illuminating purposes.

A more specific object of my invention is to devise a self-contained ultra-violet lamp provided with a standard lamp base and which may be operated directly from the ordinary 105-120 volt house lighting circuit without the use of special transformers, adapters, or other auxiliary apparatus.

A further object of my invention is to devise an ultra-violet lamp operating on a glow discharge principle and to provide means for ionizing the atmosphere of the lamp upon applying operating current so that the lamp is self-starting, and in which all parts necessary for the 0peration of the lamp from .an ordinary house,

lighting circuit are incorporated within the lamp structure proper.

My invention is illustrated in the accompanying drawing in which:

Figure 1 is an elevational view of one form of lamp according to my invention;

Figure 1a is an enlarged fragmentary View illustrating features employed in exhausting the lamp shown in Figure 1;

Figure 2! is an elevational view of a second form of lamp according to my invention; and

Figure 3 is an elevational view of a third form of lamp according to my invention.

' Referring to Figure 1, the lamp envelope comprises a bulb section la and a neck section lb formed of an insulating material transparent to both visible and ultra-violet radiations, such as known to the trade. A flare 2 is sealed to the I mounted within the bulb section la, the other end of the filament being connected to a lead wire 8 extending through the press portions of flares 2 and 3. Tube 4 thus serves as an exquartz, Corex glass, or other special glasses haust tube for section la and as a protective housing to shield wire 5 from the discharge within section lb. Mounted within section lb are two electrodes 9 and ll] preferably formed of tubular metallic material such as nickel and coated 5 with an oxide of rare earth metal to increase the electron emission capacity. Mounted within electrodes 9 and 10 are heater filaments 9a; and lea supported from insulating plugs 9b and lflb mounted in each end of the electrodes. The upper ends of heater filaments 9a and Illa are joined by wire ll, while the lower ends of these elements are connected respectively to conductors l2 and I3 sealed into the press 3a. .Electrode 9 is electrically connected to the lead wire 8, and electrode I0 is connected to lead wire l4 sealed in press 3a. The upper ends of the electrode structures are mechanically supported by wire I la joined by a glass bead to the upper end of conductor l4. 0

In manufacturing the lamp shown in Figure 1,

I prefer to assemble the entire lamp structure upon the flares 2 and 3 outside of the envelope, the two flares being mechanically connected to.- gether by tube 4 and the lower'ends of conduc- 25 tors 8, l2, l3 and I4 are left free and unconnected. Tube 4 must not be collapsed while being sealed into press portions of flares 2 and 3. The assembled structure is next inserted within the open end of the envelope and the flares 2 :and 3 are then sealed to the envelope, a suitable exhaust tube being provided at the lower end of section lb. Before placing the lamp structure within the envelope, the tubular electrodes 9 and lo are coated with a mixture of barium 35 and strontium carbonates (or other suitable solution) which by subsequent treatment is reduced to an oxide state, and to facilitate this reduction process, the conductors 8 and M are brought out through press 3a separately from conductors 4O l2 and l3 so that a suitable current may be supplied to the heater filaments to reduce the carbonate without application of a. potential to the electrodes.

Section la; is exhausted by connecting the lower end of tube 4 to the exhaust pump, and, in order to liberate occluded gases from this section'of the bulb, it is desirable to energize the filament during the exhaustion process. For this purpose the arrangement shown in Figure 50 1a is provided. In this figure the elements are shown on a greatly enlarged scale; 4a indicates a glass bead sealed around the wire 5 near the lower end and positioned within the tube 4. Within the end of a rubber tubing l5 connected to the exhaust pump (not shown) is mounted a spring Ila, on the outer end of which is mounted an iron contact block lib arranged to make electrical contactwith the lower end of wire 9. When the end of tube I5 is pressed over the end of exhaust tube 4, the contact plug lib enters the end oftube 4 and engages the end of wire I, the spring Iia serving to insure positive contact between the two elements. 11' greater pressure is required to maintain contact, a magnet may be arranged above the block lllb with the poles on opposite sides of tube 4 and the magnetic pull on the block llib will insure positive contact. The lower end of spring lie is brought out through a glass section lie of the tube It and is connected to a suitable source of current. During the exhaustion process, current is passed through the filament I by way of spring lid and conductor 5 and back to the other terminal of the source by conductor 8, the filament being operated at incandescence to drive out the occluded gases. Upon completion of the exhaustion proc- Qss, the incandescent section la is filled with an inert gas such as argon at substantially atmospheric pressure, and the section is sealed off by collapsing the tube 4 about the bead 4a and sealing the two together. The lower end of the tube 4'is then removed and the end of conductor It remains accessible for connection to the tip of the plug either directly or by means of a suitable extension welded thereon.

Section lb is exhausted in the usual manner by means of an exhaust tube (not shown) in the lower end of the section. Before the section is sealed off a small quantity of mercury is introduced into the section by any suitable method. Upon the completion of the exhausting processes and the process of reducing the coating on the electrodes, the section is sealed oil and wires 9 and I2 are Joined together at the base of bulb, and wires l9 and I4 are Joined together and connected to the sleeve of the plug 0. This completes a circuit from the sleeve of the plug through heater elements I9a, 'wire II, heater element 9a, wire I2, wire'b, filament I and wire 5 to the tip of plug 8. The filament I is designed to absorb all of the voltage drop impressed across the plug except a voltage drop of the order of 15 to volts across the combined resistance of heater elements 9a and Ila. -It is to be noted that this voltage drop is impressed between electrodes 9 and Ill. The fila-,

ment I is designed to serve as an emitter of visible light as -well as to function as a voltage reducer for theelectrodes 9 and I9. The resistance of heater elements 9a and Ila is suitably chosen to provide sufilcient heat to render the oxide coating on the electrodes thermionically active and to facilitate the establishment of a glow discharge within the section lb. The heating of the electrodes by the heater elements 9a and IOa facilitates the ionization of the mercury vapor within the section Ib and also serves to activate the oxide coating on the electrodes so that in a short time after the application of current to the lamp a glow discharge is established between the electrodes 9 and I4 which substantially fills the entire section lb. The lamp is so proportioned that the discharge is substantially that of a'diflused glow discharge as distinguished from an arc discharge which concentrates at a particular point or. points I and is especially destructive to the enemas. A

limited amount of ultra-violet radiationwill be produced in section Ia by the incandescent filament and this radiation will be aIJB ented by the presence of the argon gas, but it will be understood that this gas filling is not essential to my invention and may be omitted.

In the arrangement of the lamp shown in Figure 1 I have placed the filament I within'the section Ia having the larger radiating surface and located away from the lamp plug in order to facilj itate the dissipation of the heat produced by the filament I, which normally is several times the heat developed by the heater elements 941 and Illa. This is the preferred form of my invention, but it will be understood that the luminous filament I may be located in the neck portion lb and the electrode structures 9 and Ill may be arranged in the bulb section Ia, if desired, and this will be especially feasible where the lamp is designed to a have a low current capacity.

It will be seen that the lamp illustrated in Figure l is self-contained, self-starting, and willoperate upon any commercial supply system without any more attention than is required for an ordinary lamp. The lamp also functions as an' illuminating lamp as well as a source of ultraviolet radiations having beneficial efi'ects for many uses.

In Figure 2 I have shown a lamp designed to emit ultra-violet radiations without any substantial luminous or visible radiation. In this form of lamp, there is only one vacuum enclosure l for housing the discharge electrodes, and the voltage reducing resistances are arranged within the plug of the lamp outside of the vacuum enclosure. In this form of lamp the two discharge electrodes are formed as concentric cylindrical grid-like electrodes I6 and II, the outer electrode It being preferably formed with a wider mesh than the inner electrode I'I. These electrodes may be formed of nickel, iron, or other suitable .metal, and are supported from, the re-entrant stem I8 by suitable conductors sealed into the press of the stem. Located within the inner cylindrical electrode I1 is an ionizing or heater filament I9 the upper looped end of which is supported by a hook 20 anchored in the glass bead 20a, and the lower ends are supported from conductors I9a and I9b sealed into the press of stem l9. The filament I9 is provided with an oxide coating of the type normally employed for low current capacity vacuum tubes commonly used for radio purposes, such as barium oxide. Conductorv I'Iasupporting the electrode I'I Is connected to the shell of the screw plug 6, and

the conductor I9a leading to one side of the filament is connected to this conductor outside of the envelope I. One of the supp r ing conductors Ito for electrode I6 is connected to one terminal of a resistance element 2I located within the plug 8, and the other end of this resistance ele-x ment is connected to the ,tip contact of the plug 9. A second resistance 22 located within the plug 6 has one terminal connected to the same end of.

resistance 2l as conductor l6, and the other terminal is connected to conductor l9b leading to the filament I9. With the 'above connections it will be seen that current is supplied from the line to the filament I9 through resistances 2I and 22 connected in series, and the voltage impressed across electrodes It and I1 is equal to the combinedvoltage drop across the filament I9 and resistance 22 and is normally of the order of 15 to 20 volts. The bulb I contains a drop of mercury and is also provided with a rare gaseous filling such as neon, helium, argon or similar gases at a pressure to produce a discharge substantially entirely of the negative glow type.

3,150,054 The lamp shown in Figure 2 is normally deing. Metallic damselsigned for low power consumption; "for example, the filament is may be designed to be operated on a current of milli-ampere and with a glow discharge current of the order of 30; rnflliamperes. With these current values, resistance element 2| will berequiredto disipate only about 6' watts of energy and resistance element 22- only about one-half watt, a' line voltage of 120 volts. The operation of the lamp shownin Figure 2 will be readily understood from the operation of the lamp in Figure 1, it being understood that the filament l9 serves to heat the gas and vapor within the lamp and thereby facilitating the ionization of the vapor and the establishment of a glow discharge between elemrodes ii and H. This'glow discharge is a diffused bluish glow substantially filling the entire envelope l and is readily distinguishedirom an are or concentrated discharge. If desired, electrode i! may'also be provided with an oxide coating to facilitate the establishment of the glow discharge. This electrode may also be formed of a coated metallic tube as in Figure 1.

In either form of lamp disclosed herein the ionizing filaments, as well as the electrodes, are

- operated at temperatures below incandescence and are, therefore, not subject to the rapid deterioration which would occur if the filaments were operated at incandescence. Furthermore, in both constructions, the ionizing filament does not serve as one' of the electrodes for the ionized discharge established in the lamp, but in both arrangements these filaments are protected from the discharge by an electrode arranged to shield the filaments.

All the filaments employed in the lamps may be made of tungsten, or, if desired, the ionizing filaments may be formed of tungsten, while the filament I and resistance}! may be iormed of carbon to ofiset changes in resistance of the tungsten filaments with changes in temperature,

andthus prevent a large current upon starting the lamp.

tics of the lamp shown in Figure 1. In this arrangement the electrodes 9 and ID are constructed in the same manner as described above for Figure 1, except that resistance elements 9a and Illa are formed of higher resistance values and serve ascurrent limiting or ballast resistors in the place of the incandescent filament I in Figure 1. These electrodes are supported by conductors 9c and lllc sealedin the press of the envelope I, and the lower end of resistor 9a is connected by wire I! to the tip of the screw plug, while the lower end of resistor Illa is connected bywire I3 to the sleeve of the plug. The upper ends of the two resistors are connected to their respective electrode sleeves; In constructing this lamp, electrodes 9 and III are treated in the same manner as the electrodes for Figure Land in order to reduce the carbonate coating to an oxide, the resistor elements are heated byconnecting a. source of potential between conductors 9c--l2 and I I 0cl3 respectively. When the lampis completed, the outer ends'oi conductors 9e and lllc remain free as shown. Electrodes 9 and in are.

i also provided with a. coating of barium azide (or a tri-nitride of an'alkaline metal) in order to establish a glow discharge between the electrodes at impressed voltages-oi the order of 120 volts. This deposit may be placed on the end portions of the electrodes whichiare not coated with the oxide ,or it may be coated over the oxide coatsection, a heater filament mounted the discharge established between the two electrodes. The portions of conductors l2 and I3 extending between the press and the respective electrodes are provided with sleeves I21: and I341 to prevent the establishment of an arc discharge between these conductors. An

effective seal is formed at the ends of these insulaiingtubesbyafillingofmagnesiapaste. while this construction is not hermetically tight, it is sumcient to prevent the establishment of a discharge between the protected parts. These conductors maybe shielded in any other suitable manner as by forming tubes I In and I 3:: of metal sleeves having their upper ends. crimped around the ceramic plugs in the ends of the electrodes and their lower ends crimped around glass tube extensions surrounding the conductors and sealed into the press.

The lamp shown in Figure 3 may be modified in variousways; for example, the entire ballast resistance may be incorporated within one electrode, in which case the other electrode would not contain a resistance element and may be formed as an open mesh work cylinder surrounding the electrode containing the ballast resistance in a. manner somewhat like the arrange- I l ment shown in Figure 2. It is also obvious that The lamp illustrated in Figure 3is a modificaonly one'of the electrodes need be provided with the oxide and azide coatings, andthe oxide coating may be omitted entirely where an intense discharge is not required. If desired, the azide coating may be omitted and the discharge may be started by providing a resistance filament connected between the electrodes so as to establish a 00 -.It willbe obvious to those skilled in the art that various modifications in details and general arrangement may be made without departing from the spirit of my invention.

What I claim is:

1. An ultra-violet lamp comp g an envelope formed of material transparent to ultra-violet radiations and having a bulbous section, a neck section and a pair of terminals at the end of the neck section, a flare sealed within said envelope for hermetically separating the bulbous section from the neck section, said neck section being provided with an ionizable atmosphere, a pair 01' spaced electrodes mounted within said neck within said neck section, an incandescent filam'ent mounted in said bulbous section, connections from said terminals for energizing said heater filament and incandescent filament in serial circuit relation and for establishing a discharge between said electrodes, said connections including a conductor passing through said neck section and connecting one of said terminals to one end of said incandescent filament in the bulboussection, and means for insulating said conductor from the ionized discharge in said neck section.

' 2. An ultra-violet lamp comprising an envelope formed of material transparent to ultra-violet radiations and having a bulbous section, a neck section and 'a screw plug at the end of the neck section, a .fiare sealed within said envelope for hermetically separating the bulbous section from the neck section, an exhaust tube sealed in said flare and passing through said neck section and terminating within said screw plug, means for hermetically separating the bulbous section from the neck section, said neck section being provided with an ionizable atmosphere, a pair of spaced electrodes mounted within said neck section, a heater filament mounted within said neck section and connected across said electrodes, an exhaust tube sealed in said flare and passing through said neck section and terminating within said screw plug, an incandescent filament mounted within said bulbous section, and circuit connections from said screw plug connecting said filaments in serial circuit relation including a conductor arranged within said exhaust tube.

4. An ultra-violet lamp comprising an envelope formed oi material transparent to ultraviolet radiations and having a sealed compartment in the bulbous section, a second sealed compartment in the neck section and a screw plug at the end of the neck section, means for establishing an ionized dischargein the second sealed compartment,.an exhaust tube for the first sealed compartment passing through said second compartment and terminatingwithin said screw plug, an incandescent filament mounted within said first compartment, and circuit connections from said screw plug to said filament including a conductor arranged within said exhaust tube.

-5. An ultra-violet lamp comprising an envelope formed of material transparent to ultraviolet radiations and having a sealed compartment in the bulbous section, a second sealed compartment in the neck section and a screw plug at the end of the neck section, said second sealed compartment being provided with an ionizable atmosphere, a pair of spaced electrodes mounted within said second sealed compartment, a heater filament mounted within said second sealed compartment and connected across said electrodes, an exhaust tube for said first sealed compartment passing through said second sealed compartment and terminating within said screw plug, an incandescent filament mounted within said first compartment, and circuit connections from said screw plug connecting said filaments in serial circuit relation including a conductor arranged within said exhaust tube.

6. An ultra-violet lamp comprising a single envelope formed of material transparent to ultraviolet radiations and having a bulbous section and a reduced cylindrical neck section with a screw plug mounted at-the end o1 the neck section, a partition sealed within said envelope for separating the bulbous section from the cylindrical neck section to form hermetically separate compartments, an exhaust tube for said bulbous section passing through said necksection' and terminating in said screw plug, one of said compartments containing an ionizable atmosphere and having mounted therein a pair of spaced electrodes with a heater filament connected across the same, the other compartment having an incandescent filament mounted therein, and circuit connections from said screw plug connecting said heater filament and incandescent filament in serial circuit relation.

7. An ultra-violetlamp comprising a single en-' velope formed of material transparentto ultraviolet radiations and having a bulbous section and a reduced neck'section with a screw plug mounted at the end of the neck section, a partition sealed within said envelope for separating the bulbous section from the neck section to form hermetically separate compartments, said neck compartment being provided with an ioniz- I able atmosphere, a pair oi: spaced electrodes mounted within said neck compartment, a heater filament mounted within said neckcompartment and connected across said spaced electrodes, an

incandescent filament mounted in said bulbous o compartment, circuit connections for connecting said heater filament and said incandescent filament in serial circuit relation across the elements of said screw plug, said connections including a conductor passing through said neck compartment and connecting one end of the incandescent filament with one element 01 said plug, and means a for insulating said'conductor from the ionized discharge in said neck compartment.

PALMER H. CRAIG. 

